First of all, from the perspective of geomantic omen, coffins are associated with unlucky symbols such as death and crying, which may bring some negative emotions and influences to residents. In addition, the coffin may also emit some unclean substances, which will affect the health of the occupants.
Secondly, if the coffin is placed under the building structure, it may affect the structural stability of the building, and may even lead to damage or rupture of the building.
Finally, if the coffin is placed under the house, it may also cause psychological pressure and discomfort to the occupants. In some cultures, objects related to death may be regarded as unlucky or terrible symbols, so residents may feel uneasy and afraid.
Therefore, if there is a coffin under your house, I suggest you take appropriate measures to deal with it as soon as possible. If you are not sure how to deal with it, I suggest you consult a local feng shui master or professional to help you make a decision.